The conciliation service Acas hosted talks between London Underground and the two unions, whose members have been banning overtime. The talks will resume next Wednesday.

TSSA general secretary Manuel Cortes said: “TSSA met with London Underground at Acas to continue trying to reach a satisfactory resolution about our concerns over low staffing and a corresponding serious fall in the standard and regard for Tube safety and evacuation procedures.

Manuel Cortes (Rick Findler/PA)

“LU have said they will return to the table on January 4 with fresh and substantial proposals to alleviate the chronic understaffing on the Underground and revised details that show they intend to prioritise the safety of staff and passengers on the network.

“We await their proposals but sadly, have not so far seen or heard the resolve we have been so urgently seeking from LU bosses to reduce the high level of risk now involved in travelling or working on the Tube which was raised by the ticket office closures and the axing of 800 jobs.

“As things stand the Tube remains less staffed, less protected and less safe at the end of 2016 than at the beginning of the year. Unless LU’s fresh proposals next week give us reassurances our overstretched staff so urgently seek, our 24-hour strike will go ahead.”